Understanding the COVID-19 Vaccine Policy Terrain in Ontario Canada: A Policy Analysis of the Actors, Content, Processes, and Context

(1) Background: Canada had a unique approach to COVID-19 vaccine policy making. The objective of this study was to understand the evolution of COVID-19 vaccination policies in Ontario, Canada, using the policy triangle framework. (2) Methods: We searched government websites and social media to identify COVID-19 vaccination policies in Ontario, Canada, which were posted between 1 October 2020, and 1 December 2021. We used the policy triangle framework to explore the policy actors, content, processes, and context. (3) Results: We reviewed 117 Canadian COVID-19 vaccine policy documents. Our review found that federal actors provided guidance, provincial actors made actionable policy, and community actors adapted policy to local contexts. The policy processes aimed to approve and distribute vaccines while continuously updating policies. The policy content focused on group prioritization and vaccine scarcity issues such as the delayed second dose and the mixed vaccine schedules. Finally, the policies were made in the context of changing vaccine science, global and national vaccine scarcity, and a growing awareness of the inequitable impacts of pandemics on specific communities. (4) Conclusions: We found that the triad of vaccine scarcity, evolving efficacy and safety data, and social inequities all contributed to the creation of vaccine policies that were difficult to efficiently communicate to the public. A lesson learned is that the need for dynamic policies must be balanced with the complexity of effective communication and on-the-ground delivery of care.


Introduction
The emergence of the SARS-CoV-2 virus that causes COVID-19 sparked tremendous responses by governments across the globe [1]. The local and regional impacts of the pandemic have been highly heterogeneous, which has been true both across countries and within countries [2]. In Canada, the COVID-19 vaccination efforts began following the approval of the Pfizer and Moderna mRNA vaccines in December 2020 [3].
Canada, often described as a country with 13 different healthcare systems, is a highly decentralized federation that allows each province to enact health policies that are tailored to its local context [4,5]. The federal government provides some funding for health care, but the 10 provinces and 3 territories have developed their own policies to fund and manage their healthcare systems [6]. During the COVID-19 pandemic, this distribution of responsibility was observable in how the federal government retained responsibility for health policies related to international travel, vaccine approval, purchasing, and distribution

COVID-19 Policy Actors
The devolved nature of the Canadian government meant that a complex set of actors were involved in enacting and communicating policy decisions at the federal, provincial, and local level. The roles of the relevant actors are summarized in Table 1.

Actor Role in Communicating the COVID-19 Vaccination Response
Federal actors National Advisory Committee on Immunization (NACI) [20] -Offered recommendations in Canada for the use of and prioritization of COVID-19 vaccines.
Public Health Agency of Canada (PHAC) [21] -Provided information to healthcare professionals and the public on vaccination, gave community engagement funding through the Immunization Partnership Fund [22] and managed the Canadian Adverse Events Following Immunization Surveillance System (CAEFISS).
Health Canada [20,21] -Authorized health products for use in Canada and monitored the CAEFISS in partnership with PHAC.
COVID-19 Vaccine Task Force [23] -Guided the Government of Canada on vaccine decision making.
Minister of Health [24] -Provided leadership and support to provinces on enacting health policy

Actor Role in Communicating the COVID-19 Vaccination Response
Federal actors National Advisory Committee on Immunization (NACI) [20] -Offered recommendations in Canada for the use of and prioritization of COVID-19 vaccines.
Public Health Agency of Canada (PHAC) [21] -Provided information to healthcare professionals and the public on vaccination, gave community engagement funding through the Immunization Partnership Fund [22] and managed the Canadian Adverse Events Following Immunization Surveillance System (CAEFISS).
Health Canada [20,21] -Authorized health products for use in Canada and monitored the CAEFISS in partnership with PHAC.
COVID-19 Vaccine Task Force [23] -Guided the Government of Canada on vaccine decision making.
Minister of Health [24] -Provided leadership and support to provinces on enacting health policy and helped to ensure adequate vaccination supply.
Transport Canada [25] -Vaccine transportation for Northern and remote First Nation communities and monitored vaccine transportation policies.
Canada Border Services Agency (CBSA) [26] -Adjusted measures (including quarantine conditions) to allow for safe travel.
Public Services and Procurement Canada (PSPC) [27] -Helped to identify, procure and coordinate the delivery of COVID-19 vaccines and supplies such as needles and personal protective equipment for vaccinators.
Minister of Digital Government [28] -Introduced an enhanced digital vaccine receipt that featured a national QR code.
Health Canada's First Nations and Inuit Health Branch [29] -Launched Operation Remote Immunity to administer booster doses in Northern and First Nation communities.

Actor Role in Communicating the COVID-19 Vaccination Response
Provincial actors Ontario COVID-19 Science Advisory Table [30] -Provided weekly summaries of relevant scientific evidence for the COVID- 19 Health Coordination Table of the Province of Ontario, integrating information gathered from existing consultative bodies.
Ontario Ministry of Health [32] -Coordinated and monitored the vaccine roll-out, and developed policies to prioritize, create eligibility criteria, provide financial support to public health unit, regulate/mandate vaccination of healthcare workers, and provide billing codes to remunerate pharmacy and physician vaccination services.
Ontario Ministry of Education [33] -Introduced health and safety measures to protect against COVID-19 whilst promoting education workers to get vaccinated and supporting vaccine clinics on school sites Public Health Ontario [34] -Coordinated public health units that ran clinics and provided outreach services to isolated communities.
Ontario Community Support Association (OCSA) [35] -Established programs to support vaccine access for people who did not have access to transportation (e.g., ride programs).
Ontario Medical Association (OMA) [36] -Provided guidance and support to physicians and the public and advocated for an equitable, safe, and accessible COVID-19 vaccination framework in Ontario.
Ontario Pharmacists Association [37] -Provided training, information and support to pharmacists delivering vaccines, and collaborated with provincial stakeholders to establish a pharmacy vaccine distribution channel separate from public channels.

Community actors
Regional Hospitals in partnership with Indigenous leaders [38] -Organized earliest vaccination clinics, tested the travel logistics in Northern Ontario and support the administration of the vaccine to Indigenous and remote communities.

Public Health Units [39]
-Responsible for managing and overseeing the public outreach and primary vaccine distribution channel for each public health region in the province.
Healthcare workers (e.g., physicians, nurses, pharmacists, paramedics) [37,40] -Administered vaccines to individuals and advised patients on the safety and efficacy of the vaccines.

Processes before the Approval of Vaccines Securing Early Access to Vaccine Stocks
In October 2020, Canada contributed $220 million to procure up to 15 million vaccine doses for Canadians [41]. The Government of Canada also continued supporting domestic and new COVID-19 vaccine development by measures such as investing in Precision NanoSystems Incorporated (PNI) [42,43]. Other funding commitments included developing plans and contracts for the logistics, storage, and distribution networks that would be necessary once vaccines were licensed and available for distribution [44].

Developing Interim Prioritization Guidelines
On 3 November 2020, prior to the authorization of COVID-19 vaccines, NACI released preliminary guidance on the key populations to receive early COVID-19 vaccination in preparation for vaccine approval. [45,46]. The suggested framework included a three-phase COVID-19 vaccine rollout, starting with adults at highest-risk of severe COVID-19 health outcomes and Indigenous communities. The prioritization of Indigenous communities was based on the consideration of concerns related to equity, feasibility, and acceptability [45]. The prioritization guideline was built on the ethical values of respect for individuals and communities, beneficence and nonmaleficence, justice, and trust [47].

Vaccine Approval Processes
The approval of COVID-19 vaccines was fast-tracked through the "Interim Order Respecting the Importation, Sale, and Advertising of Drugs for Use in Relation to COVID-19", which allowed manufacturers to submit data as they became available in order to expedite the approval of new COVID-19 drugs and vaccinations [48,49]. As per the Interim Order, the information used to assess safety and efficacy was required to be made publicly available after approval, while maintaining standard labelling requirements [50]. The Interim Order also allowed "pre-positioning", which allowed manufacturers to import a COVID-19 vaccine or therapeutic product ahead of approval and place it in Canadian facilities [51]. The interim approval would then be followed by the standard Notice of Compliance, also known as the "standard approval". Manufacturers seeking a standard Notice of Compliance were required to submit a final evidence package, after which their products were added to the list of approved drugs and vaccines in Canada.
The NACI acted as independent advisors to PHAC and made recommendations to guide the use of the authorized vaccine in Canada each time a new vaccine was approved through the Interim Order [50]. PHAC promoted vaccines, and each Canadian province used the NACI guidance to enact their own vaccine policy. For example, in Ontario, the Ontario Vaccine Taskforce and the Ontario Ministry of Health used the NACI guidance statements to develop and refine eligibility criteria, which were implemented by regional vaccine task forces [52].

Processes after the Approval of Vaccines
Following the initial approval of the Pfizer and Moderna vaccines, provinces and territories were made responsible for preparing their health systems to allocate, deliver, store, distribute, and administer vaccinations, as recommended by NACI [21]. Simultaneously, Health Canada reassured provincial governments that post-vaccine surveillance would be conducted to monitor the safety and effectiveness of COVID-19 vaccines to achieve a level of vaccine coverage that would slow disease transmission and lower rates of illness, hospitalization, and death [21].
Due to the limited supplies of vaccine, Ontario began to administer vaccines at only two hospitals [53]. As supplies increased, distribution expanded to more hospitals, as well as to mobile teams, site-specific clinics, and mass vaccination clinics during "Phase 1" of vaccine rollout [54][55][56]. Supply logistics were also tested in Northern Ontario to support the administration of the vaccine to Indigenous and remote communities [37,54].
The Canadian government announcement in March and April 2021 regarding the AstraZeneca (AZ) and Janssen (Johnson & Johnson) vaccines created a serious conflict for Canadians in deciding which type of vaccine to choose [57]. In early March 2021, a lack of data on the safety and efficacy of the vaccine in people aged 65 years and older led Canadian authorities to advise against giving the AZ vaccine to this age group. However, the guidelines were further changed to re-include adults over age 65, aligning with results from observational studies in the UK about the safety of the AZ vaccine [58,59]. More concerns appeared in late March 2021, after adverse events were documented in Europe following vaccination with the AZ vaccine among adults aged below 55 years-specifically, the appearance of vaccine-induced blood clots with low levels of platelets (later termed vaccine-induced thrombotic thrombocytopenia or VITT) [60,61].
The growing awareness of risk ultimately led Ontario to halt the use of the AZ vaccine for all age groups out of an "abundance of caution" [62]. However, concerns about the shift from a focus on access and protection to a focus on risk versus benefit led Ontario's Chief Medical Officer of Health to reassure citizens that those who received their first dose with the AZ vaccine took the correct steps to prevent illness [62]. This shift made it difficult for policy makers to strike a balance between prioritizing access to early vaccinations and vaccine safety, leading Canada to introduce a controversial but responsive mix-and-match policy to allow those who had a first dose of AZ to complete their vaccine series with an mRNA vaccine [63].
As vaccine shipments continued to arrive, a hybrid approach using conventional vaccination sites and large-venue mass-vaccination sites was considered to constitute an essential innovation in curbing the COVID-19 pandemic [64]. In Ontario, primary care providers were engaged through local public health units. The Ontario Ministry of Health also established a second vaccine distribution channel in consultation with the Ontario Pharmacists Association which provided pharmacies with their own vaccine distribution chains and scheduling systems [53]. Physicians continued to work within the initial public health channel, including when administering vaccines in their own medical practices.
When Canada's COVID-19 death rate peaked on 29 April 2021, it accelerated vaccinations in remote communities [65], while Ontario allocated 50% of all available doses to 114 "hot-spot" communities [66]. PHAC expanded its Immunization Partnership Fund (IPF) to bolster COVID-19 vaccine knowledge and access for those disproportionately impacted by COVID-19 [22]. To improve access to vaccination centers, Ontario's Ministry of Transportation provided transportation to vaccination sites for people with disabilities [35,67].
Between May and September 2021, VITT was reported with the Janssen vaccine and myocarditis was observed among males vaccinated with the Moderna vaccine, creating safety concerns [68][69][70][71]. Consequently, Moderna vaccine was not made widely available to teens aged 12-17 in Ontario. From 28 September 2021, Ontarian policy also guided people aged 18 to 26 years to receive Pfizer vaccine preferentially over Moderna [72]. To encourage uptake, the Government of Ontario widened the distribution of these vaccine until it reached its peak in September 2021. Vaccination clinics in or nearby schools were opened to make vaccinations even more convenient and accessible for eligible students, their families, educators, and school staff returning to school in fall 2021 [73,74].

Communication about Vaccination Policies
Vaccination policies were communicated using four different media formats-written news releases (e.g., Ontario Newsroom), press conferences (e.g., TV channels, radio, print), social media (e.g., Twitter and Facebook), and posted policies (e.g., on government websites). At the national level, the Canadian government provided updates and communications in both official languages, English and French. The Prime Minister held frequent press conferences to inform the public on the situation and the government's response. Health Canada and the PHAC also used their Twitter and Facebook pages, TV channels, and official Government of Canada websites to communicate information, advice, and updates. At the provincial level, the Ontario government communicated the policy agenda mainly in the English language using press releases. Additionally, briefings were generally held by the Premier, the Minister of Health, and the Solicitor General, actors which also helped to present public health restrictions [75]. Additionally, a new webpage was established on 30 December 2020, by the Ontario Ministry of Health, detailing its three-phase immunization program, COVID-19 vaccines, safety measures, and approval criteria, as well as daily updates on the number of people who have been vaccinated [76]. This was carried out to help provide "transparent" communication between the public and the government [76].

Prioritization of Ontario Population Groups
As per the NACI preliminary guidance on key populations to receive early COVID-19 vaccination [45,46], three phases were implemented in Ontario as follows: Phase 1 Phase 1 included the period from December 2020 to March 2021. It focused on administering vaccines to high-risk populations such as seniors in congregate living, healthcare workers, adults in Indigenous (First Nations, Métis, and Inuit) populations, adults receiving home care, and adults aged 80 years and older [21,53,77,78].
In February 2021, "Phase 1" was accelerated, and Ontario expanded eligibility to include those aged 70 years and older [77]. Age limits were further decreased in increments such that all those aged 60 years and older were eligible for their first dose by 5 March 2021 [79,80].
Near the end of Phase 1, in March 2021, Ontario pharmacies and primary care settings joined the vaccine effort, offering the AZ vaccine to eligible Ontarians by appointments only [80].

Phase 2
Phase 2 spanned the period between April to June 2021 [79]. It included adults aged 55 years and older in decreasing increments, those living in more congregate settings where transmission could see infection rates proliferate quickly (such as shelters, adult correctional facilities, and group homes) [81], individuals with selected health conditions, certain essential caregivers, people living in "hot spot" communities with significant community spread, and those unable to work from home [21,77,78]. On 6 April 2021, "Phase 2" was accelerated, and vaccine plans started to include adults aged 50 years and older [82], and the age range of people eligible for a first dose was rapidly expanded [65] when a large quantity of vaccine arrived (over 2,621,000 vaccine doses). Pregnant people were also prioritized for COVID-19 vaccination in phase 2 when no safety issues were found [83]. The NACI had stated in earlier phases that the vaccine could be offered in pregnancy "on a case-by-case basis, if the benefits outweighed the risks and with transparency about the limited evidence available" [84]. The Society of Obstetricians and Gynecologists of Canada also issued a recommendation for vaccination during pregnancy [85].

Phase 3
Phase 3 began in May 2021, and the aim was to vaccinate all eligible Ontarians [78]. Eligible age groups were prioritized in decreasing 10-year increments on a weekly basis until all adults over 18 years old were able to book appointments [65]. In early May 2021, the Pfizer vaccine was also approved by Health Canada for adolescents aged 12 to 18 [86]. Canada was one of the first countries to approve a COVID-19 vaccine for adolescents [87].

Additional and Booster Doses
Booster doses were authorized by Health Canada on August 17, 2021, for immunocompromised people [88,89]. Health Canada aimed to restore waning immunity to a level that was deemed sufficient in individuals who had initially responded adequately to a complete primary vaccine series [89,90]. In Ontario, the expansion of groups eligible for a booster dose continued throughout the fall of 2021 until all individuals aged 18 and over were included. In addition, the recommended interval between the last dose of the primary series and the first booster dose or "third dose" was six months, but the minimum acceptable interval was decreased to three months on 20 December 2021 due to concerns about rapid spread of the Omicron variant [91].
On 15 December 2021, based on the recommendations from the Ontario Immunization Advisory Committee, a second booster dose or "fourth dose" was offered to provide additional protection in high-risk settings such as long-term care residents, retirement homes, elder care lodges, and other congregate care settings [92].

Vaccine Schedules
In anticipation of vaccine scarcity and long vaccination wait times, NACI recommended extending the interval between vaccination doses for all approved COVID-19 two-dose vaccine types on 16 March 2021 [93][94][95]. This saw extensions issued to the 2dose intervals of the Pfizer product (previously 21 days), Moderna product (previously 28 days) and AZ products (previously 28 days) [95]. Exceptions were made for those in the highest risk groups, such as people living in long-term care facilities [94]. This policy change was supported by real-world data from multiple countries that showed a good effectiveness of between 70-80% protection from a single dose of the vaccines for up to two months [93,96,97]. PHAC and other national-level stakeholders estimated that a delayed second dose policy would result in 12.1-18.9% fewer symptomatic cases, 9.5-13.5% fewer hospitalizations, and 7.5-9.7% fewer deaths in the population over a 12-month time horizon [98].
In January 2021, due to vaccine shipment delays and based on NACI's recommendations, the Ontario Ministry of Health rescheduled all second dose appointments for the Pfizer vaccine to follow 35 days after the first dose, and to come no later than 42 days, for all vaccine recipients other than residents of long-term care, high-risk retirement, and First Nations elder care homes [99][100][101]. However, the policy was complicated when the Delta variant emerged [102,103]. Despite these challenges, Canada's vaccination rate surged, and by July over 70% of the population had received at least one shot, with decreased infection and hospitalization rates [98].

Vaccine Mandates Vaccination and International Travel
The decision to encourage Canadians to receive different COVID-19 vaccines once the AZ vaccine was retracted caused international travel difficulties [104][105][106]. Several countries, including the United States, only considered persons to be completely vaccinated if they had received two doses of the same vaccine [107]. Furthermore, the specific "Covishield" brand of the AZ vaccine made in the Serum Institute of India, which was one of the AZ vaccine brands administered in Canada, was not on the list of approved vaccines in many European countries, leading to the implementation of travel restrictions for recipients of this vaccine [107].
The Canadian government's policies to open the borders for international travel were implemented in several phases. The first phase began on 5 July 2021, when fully vaccinated travelers were exempted from quarantine and testing requirements [108,109]. The second phase, starting on 7 September 2021, required a pre-arrival PCR test and submission of a quarantine plan via the ArriveCAN online system [110]. The third phase started on 7 November 2021 and indicated that fully vaccinated people returning to Canada were no longer required to provide a negative PCR test if their trips had been for less than 72 h, but still had to provide an ArriveCAN receipt [111]. However, additional travel restrictions were introduced for foreign nationals returning to Canada with the emergence of the Omicron variant in late November 2021 [112,113].

Vaccination and Public Settings
Canada shifted towards implementing mandatory vaccination requirement policies for specific groups in early September 2021. On 7 September 2021, Ontario issued a directive mandating hospitals, long-term care homes, and community care service providers to adopt a COVID-19 vaccination policy for employees, staff, contractors, students, and volunteers [74].
By September 2021, the provincial governments started to plan for a return to in-person gatherings and activities and to minimize the disruption to businesses [114]. For example, the Government of Ontario announced the launch of a provincial vaccine certificate system, which required proof of vaccination for entry to certain settings such as restaurants, bars, and nightclubs, and increased capacity limits up to 75% [115,116]. With public health and healthcare indicators remaining stable and the proof of vaccination requirements in effect, Ontario lifted further capacity limits, allowing 100% capacity for indoor settings and events on 9 October 2021 [117].
Restrictions related to COVID-19 vaccine requirements continued to evolve and by 29 October, 2021, federal public servants were required to confirm their vaccination status [118]. In addition, the use of the enhanced COVID-19 vaccine certificates with QR codes was required to show proof of vaccination from 4 January 2022 [92].

COVID-19 Policy Context
The COVID-19 vaccination policies in Ontario, Canada, as outlined above, were influenced by a variety of contextual factors, which we have categorized as situational, social, structural, and international factors.
Situational factors are external factors that influence policy decisions. In the reviewed policies, the situational factors included the initial results of evidence-based clinical trials; real-world effectiveness data for the first vs. second dose of 2-dose vaccines and the duration of protection following the first dose; modelled impact of rapidly vaccinating a greater number of people with one dose; real-world data on the risk of severe illness and death; perceived and measured risks of transmission to vulnerable populations; emerging safety data on vaccines and boosters; evolving understanding of the effect of the vaccine on preventing transmission; number and type of available vaccines; COVID-19 caseloads and deaths; and new and emerging SARS-CoV-2 variants [46,119].
Social factors influence policies and actions that might affect vaccine access and individuals' vaccination beliefs and choices [120]. The social factors identified in the policies included public health literacy, the social media role in promoting awareness, and collaboration with different stakeholders at national, municipal, and provincial levels.
Structural factors are the broader political, economic, and environmental conditions that influence vaccination policies. The structural factors identified in the policy review of COVID-19 vaccines in Ontario included a focus on distribution, logistics, and administration; clinical supervision and surveillance; statistics; case reporting; and public education and awareness [77] Finally, international factors influence the development of vaccination policies between countries and include the role of scientific and expert evidence in implementing travel restrictions; federal legislation; regulation and enforcement of international travel measures; and compliance with international organizations, such as the WHO and US Center for Disease Control, and their guidelines in travel restriction policy and decision making [109,121].

Discussion
Using the policy triangle framework, our analysis revealed four major findings. Firstly, prior to the emergence of the Omicron variant of concern, Canada's COVID-19 vaccination policies were based on the principles of equity, feasibility, and acceptability. Secondly, the implementation of equitable prioritization frameworks was challenging in the context of decentralized government and vaccine scarcity. Thirdly, rapid policy changes related to the AZ vaccine, extended dose intervals, and the vaccination of adolescents were effective at maximizing benefit and limiting harm. However, they complicated equity efforts. Finally, efforts to communicate the evolving policies and to build vaccine trust relied on providing coordinated messages, advice, and new evidence through different media formats.
In our policy review, it was clear that Canada's controversial policy to increase the interval for administration of second doses achieved its goal of giving a first dose to more people in a shorter period. However, it also contributed to considerable logistical and communication challenges during a very fraught time [122]. Such policy decisions show how under non-ideal circumstances-such as a limited vaccine supply in the context of the emergence of a more infectious variant of concern-the risk/benefits of delaying the second dose outweighed the risk/benefit of providing a second dose on time [123].
However, Boucher and colleagues have argued that extending the interval between doses may have only been effective in protecting younger populations, not older adults, and that sticking to the original dosing schedule might have resulted in fewer COVID-19-related deaths [124]. Furthermore, previous studies have shown that older adults may have a lower immune response to a single dose of mRNA vaccination than younger ones, and the efficacy of one dose in reducing hospitalizations was lower in adults aged 75 and older than in younger populations [125][126][127]. Thus, in addition to contributing to research highlighting the potential impacts of delayed dosing intervals on vaccine effectiveness, our analysis also highlights that frequent policy changes may have hurt policy clarity and communication and shaken confidence in policy decision makers' knowledge and authority.
It should be noted that by August 2021, Canada was seen as a global leader in achieving high COVID-19 vaccine uptake, having vaccinated an estimated 75% of the population aged 12 years and over [128]. However, prior to the fall of 2021, there were considerable challenges that benefit from closer examination and reflection. In one comparative analysis of COVID-19 emergency plans in Ontario, Québec, and British Columbia, the decentralization of multi-level governance was found to be confusing and problematic as authority boundaries for different elements crossed, leading to heterogenous responses [129]. Another Canadian study that compared COVID-19 vaccine policies between Canada and Israel highlighted that early Canadian COVID-19 vaccine policy was hurt by decentralized policy making, incoherent emergency planning, and a weakened primary health care system [130]. However, none of these studies discussed how Canada's roll-out of vaccines was framed consistently around the need for equity during a period of vaccine scarcity. Canada's framework was nuanced, difficult to communicate and implement, but it reflected a growing awareness of the role of systemic racism in health disparities. In a report in which we compared Canada's vaccine policy and communication with that of the UK, it was noted that policy makers in the UK did not explicitly prioritize equity as they were not limited by vaccine scarcity as much as Canada was [18].
In the context of a global pandemic, safety concerns surrounding the AZ vaccine may have caused a "triggering event," disrupting standard policy making and resulting in the implementation of conflicting policies at different government levels. NACI, which had consistently recommended that the Pfizer and Moderna mRNA vaccines be offered as the preferred vaccines over AZ in Canada, was widely criticized for causing vaccine hesitancy, confusion, and delays to vaccine access in a time of significant vaccine scarcity [131]. Significant efforts were seen worldwide to support 'quick-fix' vaccination programs capable of tackling COVID-19, regardless of the type of vaccine used. However, in Canada, safety ultimately prevailed as the dominant framework. In line with our findings, other studies have insisted that lingering concerns about AZ's efficacy and safety, as well as inconsistent communication from Health Canada and NACI, influenced vaccine acceptance [132]. Moving forward, the top-down approach to policy making seen in Canada may need to be reassessed to ensure that the pragmatic concerns of grassroots actors are reflected in the policies they will have to implement.
A controversial action undertaken in Canada was the adoption of vaccine mandates. The federal government focused on mandates related to travel, while provincial governments focused on mandates for public spaces. These restrictive policies sparked protests and ignited a fierce debate over how countries curtail individual liberties in the name of public health [133]. The success of vaccine mandates remains contentious. A study by Karaivanov and colleagues reported that the announcement of a mandate was associated with a rapid and significant surge in new vaccinations across Canadian provinces [134]. In comparison, other researchers have questioned the paradigm that existed around stringent global testing, vaccine mandates, and travel restrictions. They claim that applying enforced and intrusive policies fueled vaccine hesitancy [135]. As the mandates were beginning, Flood et al. noted that the mandates could be challenged under the Canadian Charter of Rights and Freedoms, but predicted that governments could likely defend the mandates. [136]. Our analysis highlights how the mandates were designed to create simple and clear instruction to protect health and welfare but that they were in fact complex to implement, with both the federal and provincial governments being responsible for different types of mandates and related layers of non-inclusion provisos and guidance.

•
Vaccine scarcity can make it very difficult to develop and implement stable and equitable policies, especially in the context of a public health emergency. • It is critical for policy makers, including those providing high-level guidance documents, to engage with local public health officials, frontline health workers, and community leaders to anticipate the impacts of rapid policy changes in the context of a public health emergency. • Vaccine policies naturally change as new safety and efficacy data emerges; however, this can impact trust among marginalized groups who are prioritized early before safety and efficacy data are fully available.

•
In a pandemic the science evolves rapidly, and policy makers need to be cautious while communicating certainty about the risks and benefits of vaccination.

Implications for the Public
In the COVID-19 pandemic, vaccine policies needed to be made quickly in the context of limited information and then continuously refined as new vaccines and vaccine data emerged. Canada is well known for some controversial vaccine policies during this time, such as allowing Canadians to receive different vaccine brands, delaying the second vaccine dose, and the decision to use and then stop using the Oxford/AstraZeneca vaccine. This study found that the factors that led to Canada's complex and dynamic policies included Canada's multi-level federated health system, its very limited vaccine manufacturing capacity, and its desire to produce equitable policies that prioritized the vaccination of citizens at highest risk of developing severe cases of COVID-19.

Strengths and limitations
By using a policy triangle framework built on the four essential dimensions of content, context, process, and actors, we were able to conceptualize COVID-19 vaccination policies. This allowed us to perform a detailed exploration of the landscape around policy decisions and analyze vaccination policy decisions in the context of the evolving COVID-19 pandemic and Canada's devolved government. However, because our policy search ended in December 2021, any policies linked to childhood immunization which began at the end of 2021 were not included or analyzed. Further, due to Canada's federated healthcare system, there were very few national policies established. We found it critical to limit the scope and scale of the review to a single Canadian province to ensure that policies, ranging from those of the federal government to those of local actors, could be examined in detail. The province of Ontario was selected to be the exemplar province as it is Canada's largest province. Future research examining other jurisdictions would be beneficial, such as in the smaller Atlantic provinces or rural and remote Northern territories. Finally, this research described policies prior to the emergence of the Omicron variants of concern. This heightened the urgency of the COVID-19 vaccination and led to the development of new vaccination tactics such as serial boosters and post-infection anti-viral treatments.

Conclusions
The Canadian experience demonstrates how it can be difficult to develop priority access frameworks that keep both vaccine safety and efficacy as core principles-especially in a federated health system, in the context of vaccine scarcity, and during a pandemic involving a novel virus with novel therapeutics. Safety concerns about the AZ vaccine and overall vaccine scarcity led to a complex evolution in policy decisions, including the development of longer vaccination intervals, a preference for mRNA vaccines, and mixed vaccine schedules. The challenges of making and implementing these policies in rapidly changing circumstances have been frequently underestimated. The policy streams in Canada's vaccine roll-out demonstrate how the broad problems of enormous global vaccination demand could come into conflict with more traditional vaccination considerations such as risk and benefit assessment. Acknowledgments: Thank you to the community members who met with the research team through the early pandemic vaccine response to help us understand the questions that were most important to ask and answer.

Conflicts of Interest:
The authors declare no conflict of interests. Mandatory vaccination for the federally regulated air, rail, and marine sectors helps limit the risk of spreading the Delta variant COVID-19 and helps prevent against future outbreaks.
All federal employees in the Core Public Administration must prove their immunization status. Otherwise, they will be placed on administrative leave without pay beginning November 2021.